This invention pertains to the art of electric lamps and more particularly, to a reflector type lamp having improved resistance to mechanical shock and vibration. The invention is particularly applicable to a parabolic aluminized reflector (PAR) lamp and will be described with reference thereto. However, it will be appreciated that the invention has broader applications and may be advantageously employed in related environments and applications.
PAR lamps are well known in the art for providing general spot or flood lighting applications. These lamps commonly employ a light source mounted within an internal reflector cavity at a location approximately at the optical focal point of the reflector. The light source may be an incandescent source, such as a tungsten halogen light source, or an arc discharge light source such as a ceramic metal halide or CMH lamp. Of course other incandescent or discharge light sources have also been used.
The light source is typically secured with an adhesive at a narrowed end of the reflector cavity. That is, the light source is cantilever mounted in the reflector. A bonding material, such as a curable adhesive or cement, is used to secure the light source to the reflector in these types of lamp assemblies. This is the sole manner of mounting the light source in the reflector cavity and the arrangement must withstand mechanical shock and vibration both during lamp manufacture, shipment, and subsequent lamp service.
An auxiliary support is shown, for example, in commonly assigned U.S. Pat. No. 4,959,583, the disclosure which is hereby incorporated by reference. Another commonly owned patent, U.S. Pat. No. 5,057,735, illustrates a similar lamp assembly also intended to address the shock and vibration resistance of the assembled lamp unit. Again, the details of the '735 patent are hereby incorporated by reference. A closure member is interposed between the narrow end of the reflector cavity and the press seal region of the light source. The closure member is of reduced height and incorporates an exhaust passage for evacuating the reflector cavity, an arrangement that has met with widespread commercial acceptance.
Still another arrangement for securing the light source to the reflector, while addressing shock/vibration, enlarges the opening in the base of the reflector cavity and slides a thin metal closure member over the press seal region of the lamp base. This configuration allows the light source to be moved downwardly in the reflector whereby the source is more closely aligned with the focal point of the reflector.
Rather than modifying the lamp assembly, another proposed solution has been to improve shock and vibration resistance during shipment and handling by modifying the lamp packaging. However, as may be expected, the improved performance offered by the modified packaging adds to the overall cost of the lamp since the specialized packaging costs more. Moreover, modified packaging still does not resolve shock and vibration resistance concerns during assembly.
Accordingly, there is still a perceived need for improving the durability of the lamp assembly, particularly to mechanical shock and vibration, without an attendant significant increase in cost.